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Dynamic covalent polymerisation of boron-aromatic oligomeric monomers

Final Report Summary - OLIGOMERS-POLYMERS (Dynamic covalent polymerisation of boron-aromatic oligomeric monomers)

Developed a new and general strategy for one pot self-assembly synthesis of polypseudorotaxanes (P1-3) and corresponding three model rotaxanes from easily accessible subcomponents (Scheme 1). These new polymers and model compounds were well characterized by NMR (1H & 13C) spectra, mass spectra and elemental analysis. We have also presented the Xray single crystal structures of two model compounds. The chain lengths of these polymers were determined by DLS measurements and also supported by end group analysis of 1H NMR spectra. Those polymers show redox active, very high stability in the oxidized state, and a well-defined spectroelectrochemistry. Incorporation of extended conjugation via phenyl ring in the polymer backbone, which did not leads to significant and predictable changes in the electrochemical and optical properties.

The polymers P1-3 do not show any solution to gel formation behaviour upon heating in DMSO up to 150°C. The polymers P2-3 easily converted to corresponding phosphine ligand containing polymers P4-5, when these polymers P2-3 were subjected to react with 1.2 equivalent of bis[2-(diphenylphosphino)phenyl]ether (POP) ligand in DMSO at room temperature (Scheme 2). In contrast to polymer P1-3, the phosphine ligands containing polymers P4-5 showed solution to gel formation behaviour upon heating the polymer in DMSO at low temperature (70°C).

We have synthesized a new type copper(I) coordination materials having arylphosphine ligand and imine chelate ligand by self-assembly condensation strategy for phosphorescent active materials for organic light emitting devices (OLEDs). The general protocol to prepared these Cu(I) complexes and polymers from the condensation of amine, pyridine carboxaldehyde and bis[2-(diphenylphosphino)phenyl]ether (POP) ligand in the presence of Cu(MeCN)4BF4 is shown in Scheme 3.

First time, we presented the X-ray structure of few copper(I) metal complexes (Figure 1). 1H NMR and DLS study of these polymers established the formation of long polymer chain. The optical and electrochemical properties of the Cu(I) complexes and polymers were systematically studies by UV-vis spectroscopy and cyclic voltammetry. This study of Cu(I) materials with diphosphine ligands shows that the structure of the ligand is important in defining the optical as well as stability, chemical and physical properties.

Few of these Cu(I) polymers showed a transition from solution to gel in DMSO when the temperature of the solution was increased to 70°C (Figure 1). This process is accompanied by a color change from deep red to light yellow (Figure 2). The gel obtained at low temperature is highly stable, and worked at low critical gelation concentration (1.2% w/w) in wide range of solvents namely DMSO, DMF etc. The low temperature of gelation was confirmed by systematic studies by variable temperature 1H NMR and the “sol to gel” transition may be behaved as a quasi reversible process at right condition. The percentage of cross link and possible structures of the resulted gel were established by NMR studies.

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